Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/02—Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
  • A61B5/026—Measuring blood flow
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/02—Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
  • A61B5/026—Measuring blood flow
  • A61B5/0261—Measuring blood flow using optical means, e.g. infrared light
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/117—Identification of persons
• • G—PHYSICS
  • G06—COMPUTING; CALCULATING OR COUNTING
  • G06V—IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING
  • G06V40/00—Recognition of biometric, human-related or animal-related patterns in image or video data
  • G06V40/40—Spoof detection, e.g. liveness detection
  • G06V40/45—Detection of the body part being alive
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/117—Identification of persons
  • A61B5/1171—Identification of persons based on the shapes or appearances of their bodies or parts thereof
  • A61B5/1172—Identification of persons based on the shapes or appearances of their bodies or parts thereof using fingerprinting
• • G—PHYSICS
  • G06—COMPUTING; CALCULATING OR COUNTING
  • G06V—IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING
  • G06V40/00—Recognition of biometric, human-related or animal-related patterns in image or video data
  • G06V40/10—Human or animal bodies, e.g. vehicle occupants or pedestrians; Body parts, e.g. hands
  • G06V40/14—Vascular patterns

Definitions

• This invention relates to a method and apparatus for detecting blood flow in subcutaneous veins present at a portion of a user's body, wherein radiation is directed at the user's body portion, and radiation reflected thereby is received and analyzed.
• Fingerprint techniques in particular are very popular because of their user-friendliness and convenience. However, such techniques are very susceptible to forgery for two main reasons. Firstly, fingerprints are easy to replicate (in, for example, gelatin or the like) and secondly they can be relatively easily "stolen", even breathing on conventional fingerprint sensors can result in an erroneous verification. It has been found that the pattern of subcutaneous blood vessels is characteristic of an individual and the fact that blood- vein patterns in the hand can be used as a unique "fingerprint" has been illustrated in US Patent No. 5,787,185. US Patent No.
• 4,699,149 describes apparatus for identifying an individual in which a user's body portion is irradiated by radiation to which the skin is translucent, and the location of blood vessels is detected by means of a differential temperature measurement, for example, or using techniques such as nuclear magnetic resonance or acoustic monitoring of the pulse.
• a differential temperature measurement for example, or using techniques such as nuclear magnetic resonance or acoustic monitoring of the pulse.
• many types of systems are susceptible to forgery through the use of fake or non-living fingerprints. It is therefore an object of the present invention to alleviate the problems outlined above, and provide apparatus for detecting blood flow in subcutaneous veins.
• apparatus for detecting blood flow at a portion of a user's body, the apparatus comprising at least one laser, having a laser cavity, for generating a measuring beam arranged to be focused or converged at a point beneath the epidermis of said user's body portion, wherein at least some of the measuring beam radiation reflected by blood flowing in subcutaneous veins at said user's body portion re-enters said laser cavity, the apparatus further comprising measuring means for measuring changes in operation of said laser cavity caused by interference of reflected measuring beam radiation re-entering said laser cavity and the optical wave in said laser cavity, and means for providing an electric signal representative of said changes, said changes containing data relating to blood flow in said subcutaneous veins at said user's body portion.
• the present invention extends to a heart rate monitor including apparatus for detecting blood flow as defined above. Also in accordance with the present invention, there is provided a method for detecting blood flow at a portion of a user's body, the method comprising generating, using at least one laser having a laser cavity, a measuring beam arranged to be focused or converged at a point beneath the epidermis of said user's body portion, wherein at least some of the measuring beam radiation reflected by blood flowing in subcutaneous veins at said ' user's body portion re-enters said laser cavity, the method further comprising measuring changes in operation of said laser cavity caused by interference of reflected measuring beam radiation re-entering said laser cavity and the optical wave in said laser cavity, and providing an electric signal representative of said changes, said changes containing data relating to blood flow in said subcutaneous veins at said user's body portion.
• Means may be provided for measuring a variation of impedance of the laser cavity.
• the measuring means may comprise a radiation detector for detecting radiation emitted by the laser.
• means may be provided for detecting blood flow at a plurality of positions within the user's body portion.
• a plurality e.g. a one- or two-dimensional array
• means may be provided for causing relative movement between the measuring beam and the user's body portion. In its simplest form, of course, this may be the ability to scan the user's body portion with the apparatus and/or the ability to allow the user to move, for example, their fingertip across a measurement area of the apparatus.
• the measuring beam may comprise infra-red radiation, and the apparatus is preferably arranged and configured to detect blood flow in multiple directions.
• a spectrum of reflected radiation may be generated and the apparatus beneficially comprises means for detecting the spectral width of reflected measuring beam radiation in order to identify blood flow in multiple directions.
• the wavelength of the measuring beam radiation may be selected so as to penetrate the epidermis of the user's body portion to a predetermined depth.
• Optical means may alternatively, or in addition, be provided for focusing or converging the measuring beam radiation at the above-mentioned point beneath the epidermis of the user's body portion.
• Imaging means may be provided for creating from the electric signal an image of one or more veins present in the user's body portion corresponding to the detected blood flow therein.
• the user's body portion may comprise a fingertip
• the present invention extends to a fingerprint detection system including apparatus for detecting blood flow, as defined above.
• the apparatus may be incorporated in a known fingerprint detection system to simply provide a "liveness" detector, i.e. if there is no blood flow, then the fingertip is not live.
• Means may be provided for determining, from the detected blood flow, the user's heart rate and, in fact, as stated above, the invention extends to a heart rate monitor including apparatus for detecting blood flow as defined above.
• Fig. 1 is a schematic diagram of a blood flow detector according to an exemplary embodiment of the present invention
• Fig. 2 is a schematic diagram of a blood flow detector according to another exemplary embodiment of the present invention, in which a one- or two-dimensional array of Doppler sensors is employed.
• a phenomenon known as "self-mixing" in a laser diode is utilized in the present invention for the purposes of detecting blood flow. This phenomenon is used in a known arrangement for detecting movement of a fingertip relative to a sensor in an optical input device, as described in detail in International Patent Application No.
• a diode laser having a laser cavity is provided for emitting a laser, or measuring, beam.
• the device is provided with a transparent window across which an object, for example a human finger, is moved.
• a lens for example, a plano-convex lens is arranged between the diode laser and the window. This lens focuses the laser beam at or near the upper side of the transparent window. If an object is present at this position, it scatters the measuring beam.
• a part of the radiation of the measuring beam is scattered in the direction of the illumination beam and this part is converged by the lens on the emitting surface of the laser diode and re-enters the cavity of this laser.
• the radiation re-entering the cavity of the diode laser induces a variation in the gain of the laser and thus in the intensity of radiation emitted by the laser, and it is this phenomenon which is termed the self-mixing effect in a diode laser.
• the change in intensity of the radiation emitted by the laser can be detected by a photo diode, provided for this purpose, which diode converts the radiation variation into an electric signal, and electronic circuitry is provided for processing this electric signal.
• Movement of the object relative to the measuring beam causes the radiation reflected thereby to undergo a Doppler shift.
• This frequency shift is dependent on the velocity with which the object moves and is of the order of a few kHz to MHz.
• the frequency-shifted radiation re-entering the laser cavity interferes with the optical wave, or radiation generated in this cavity, i.e. a self-mixing effect occurs in this cavity.
• the interference will be constructive or negative, i.e. the intensity of the laser radiation is increased or decreased periodically.
• the frequency of the laser radiation modulation generated in this way is exactly equal to the difference between the frequency of the optical wave in the cavity and that of the Doppler-shifted radiation re-entering the cavity.
• the frequency difference is of the order of a few kHz to MHz and thus easy to detect.
• the combination of the self-mixing effect and the Doppler shift causes a variation in behavior of the laser cavity; especially its gain or light amplification varies.
• the impedance of the laser cavity or the intensity of the radiation emitted by the laser may, for example, be measured, and not only can the amount of movement of the object relative to the sensor (i.e. distance traveled) be evaluated, but the direction of movement can also be determined, as described in detail in International Patent Application No. WO 02/37410.
• a laser diode 10 for detecting blood flow by means of laser Doppler shift, there is provided a laser diode 10, a monitor diode 12, a beam splitter 14 and a focusing lens 16 for focusing the radiation beam ' 18 emitted by the laser diode 10 to a point below the epidermis of a subject's fingertip 20.
• Coherent light reflected back and re-entering the laser cavity of the laser diode 10 will lead to a measurable intensity modulation of the laser caused by laser feedback and self-mixing, which can be measured using the monitor diode 12, and processed in the manner described above.
• the fingertip it is possible to generate a complete image of blood flow in the veins of an area of the subject's body under consideration (in this case, the fingertip), using a one-dimensional array of single-pixel detectors with relative movement of the array and the fingertip (either by scanning the stationary fingertip with the detector or moving the fingertip across the stationary array), or using a two-dimensional array of detectors (in which case, the fingertip can simply be placed relative to the array and both can be held stationary while the required measurements are carried out).
• multiple photo diodes may be provided in respect of a single measuring beam to detect changes in the laser cavity caused by light reflected from different layers of veins beneath the subject's skin, although an adequate blood flow measurement could be obtained using a single photo diode appropriately located relative to the laser diode.
• the diode laser 10 of the arrangement of Fig. 1 is an edge emitting diode laser
• the beam splitter 14 is unnecessary because the monitor diode 12 is located behind the laser diode 10 and a [art of the light is emitted backwards.
• VCSEL Very Cavity Surface Emitting Laser
• a NCSEL and a separate photo diode may be placed in one housing, and although no beam splitter needs to be used, a housing output window is arranged and configured to reflect light onto the monitor diode.
• the present invention can be used to provide a fingerprint sensor system in itself, which is very robust against forgeries.
• integrating a system, such as that illustrated schematically in Fig. 1 of the drawings, in a conventional fingerprint sensor results in a fingerprint sensor system which is more robust against security attacks and/or forgeries.
• the system of the invention is simply employed as a "liveness" detector, and the spot of the measuring beam is ideally positioned in the image field of the fingerprint, which can be realized either by using optical beam splitters or by integrating the liveness detector and fingerprint sensor into a single chip, for example.
• the advantages associated with the present invention are numerous, and include the fact that the liveness detection is contactless and detects blood flow in and under the subject's skin.
• the system of Fig. 1 can be miniaturized and can therefore be made very small and at a very low cost.
• the laser diode 10, monitor diode 12 and signal processor can be integrated on silicon and the required lens can be, for example, glued on top of the chip.
• the signal processing employed in the liveness detector may be arranged and configured such that it can discriminate between uni-directional movement and movement in many different directions, which is much more typical of the blood flow in a vein network. In general, such multiple movements will result in a widening of the laser spectral peak, which can be detected virtually instantaneously.
• the system of the present invention (by relatively simple implementation of the signal processing) to distinguish between a single, one-directional movement (in the case of forgery), which results simply in a shift of the laser spectral peak, and a more complex pattern of multiple movements in the case of a genuine, live fingerprint, in which case there is a determinable widening of the laser spectral peak.
• a second exemplary, multi-pixel system for detecting blood flow by means of laser Doppler shift there is provided a one- or two- dimensional array of VCSEL diodes 10a - 1 On (numbered vcsel 1....N in the case of a one- dimensional array, or vcsel 1*1....n*m in the case of a two-dimensional array), and a focusing lens 16 for focusing the radiation beam 18 emitted by the laser diode 10 to an image plane 22 below the epidermis 24 of a subject's fingertip.

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• Health & Medical Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Pathology (AREA)
• Surgery (AREA)
• Veterinary Medicine (AREA)
• Public Health (AREA)
• General Health & Medical Sciences (AREA)
• Animal Behavior & Ethology (AREA)
• Molecular Biology (AREA)
• Biophysics (AREA)
• Medical Informatics (AREA)
• Biomedical Technology (AREA)
• Heart & Thoracic Surgery (AREA)
• Physiology (AREA)
• Cardiology (AREA)
• Hematology (AREA)
• Human Computer Interaction (AREA)
• General Physics & Mathematics (AREA)
• Theoretical Computer Science (AREA)
• Multimedia (AREA)
• Measuring Pulse, Heart Rate, Blood Pressure Or Blood Flow (AREA)
• Measurement Of The Respiration, Hearing Ability, Form, And Blood Characteristics Of Living Organisms (AREA)

Priority Applications (5)

Applications Claiming Priority (2)

Publications (1)

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• 2005
  • 2005-04-26 CN CN2005800136369A patent/CN1950027B/zh active Active
  • 2005-04-26 WO PCT/IB2005/051356 patent/WO2005104935A1/en not_active Application Discontinuation
  • 2005-04-26 KR KR1020067022136A patent/KR101123179B1/ko active IP Right Grant
  • 2005-04-26 JP JP2007510214A patent/JP4772036B2/ja active Active
  • 2005-04-26 EP EP05732776.9A patent/EP1744669B1/de active Active
  • 2005-04-26 US US11/568,395 patent/US7708695B2/en active Active
  • 2005-04-28 TW TW094113764A patent/TW200605847A/zh unknown

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